This invention relates to a park brake actuator system for a vehicle. As is well known, vehicles often comprise a park brake system for preventing undesirable inadvertent motion of the vehicle when it is not in use. Park brake systems of vehicles generally comprise one or more braking components and one or more braked components complimentary to each of the one or more braked components. The braking component of each complimentary pair of a braking component and a braked component is anchored to either the superstructure of the vehicle or a drivetrain of the vehicle. The superstructure of a vehicle being the main strength providing structure of the vehicle which provides support for and ensures proper relative location of a large percentage of the other components of the vehicle. For vehicles of body-on-frame construction the superstructure of the vehicle is a frame of the vehicle and for vehicles of unibody construction the superstructure is the main body structure of the vehicle. The braked component of each complimentary pair of a braking component and a braked component is anchored to whichever of the superstructure of the vehicle and the drivetrain of the vehicle its complimentary braking component is not anchored to. More specifically, which ever of the braking component and the braked component is anchored to the drivetrain of the vehicle is anchored to a working component of the drivetrain. For purposes of this disclosure a working component of the drivetrain of the vehicle is defined to be a component that must move relative to the superstructure of the vehicle in order for the vehicle to travel along the ground. As is well known, at least one of the braking component and the braked component of a parking brake system of a vehicle generally has attached to it friction material as is well known. Parking brake systems are constructed in such a manner that the braking component of the parking brake can be selectively maintained in a released position in which it is not in contact with the braked component or driven into and maintained in a set position in which the friction material that is attached to the braking component and/or the braked component is forcibly compressed between the braking component and the braked component. When the braking component is in its released position the parking brake system presents little to no resistance to movement of the working components of the drivetrain of the vehicle relative to the superstructure of the vehicle and, therefore presents little to no resistance to travel of the vehicle. When the braking component is in its set position frictional forces between the braking component, the braked component and the friction material between them resists relative motion between the braking component and the braked component and thus relative motion is resisted between the superstructure of the vehicle and the drivetrain of the vehicle and travel of the vehicle is resisted. When the one or more braking components of a park brake system are in their released position, the park brake system is in its released operational state, and an individual can operate the vehicle freely. When an individual desires to prevent undesirable inadvertent motion of a vehicle that is parked they can effect a set operational state of the park brake system by operating the park brake system to drive the one or more braking components of the park brake system to their set position and maintain them there. When the park brake system is in its set operational state in such a manner, it prevents the vehicle from inadvertently moving.
The mechanisms of park brake systems that drive the one or more braking components of the park brake system between their set and released positions and maintain them in those positions can have many different constructions. The present invention is particularly related to those park brake systems that have connecting linkages between the one or more braking components of the park brake system and a park brake actuator of the park brake system. Such park brake systems are generally constructed such that, when an individual moves the park brake actuator in an engaging direction, the connecting linkages are caused to move in a disengaging direction and the one or more braking components of the park brake system are caused to move toward their set position by the connecting linkages. The construction of such park brake systems is such that when the park brake actuator is moved in a disengaging direction, which is opposite the engaging direction, the connecting linkages are allowed or caused to move in a disengaging direction opposite their engaging direction. When the connecting linkages move in their disengaging direction the one or more braking components of the park brake system are either allowed to or are caused to move toward their released position by the connecting linkages. Most such park brake systems also generally comprise one or more return springs each of which is attached at one end to the superstructure of the vehicle and at the other end to braking components or connecting linkages of the park brake system. The construction of these park brake systems is such that the return springs bias the connecting linkages toward their disengaging direction which, in turn, bias the park brake actuator toward its disengaging direction. As a result, when an individual moves the park brake actuator of such a system in the engaging direction they must overcome the resistance provided by the return springs. Also, in order to maintain the one or more braking components in their set position, forces must be applied to the connecting linkages and/or the park brake actuator to balance the force applied by the return springs and prevent them from driving the connecting linkages and the park brake actuator in their disengaging directions. Most such park brake systems further include latching mechanisms for balancing the forces applied by the return springs to the connecting linkages when the braking components are in their set position so that the braking components can be maintained in their set position without an individual""s attention. When an individual releases these latching mechanisms of the park brake system and subsequently releases the park brake actuator, the return springs drive the connecting linkages and the park brake actuator in their disengaging directions and allow or cause the braking components to travel to their released position. Many such park brake systems also have a return stop which is engaged to the superstructure of the vehicle and which contacts some part of the connecting linkages or the park brake actuator as they travel in their disengaging directions and limits the range of travel of the connecting linkages and the park brake actuator in their disengaging direction. For purposes of this disclosure the portion of the connecting linkages or the park brake actuator which contacts the return stop and limits the travel of the connecting linkages in their disengaging direction will be referred to as the return bumper of the park brake system. The return bumper may be any of a number of different portions of the connecting linkages or the park brake actuator. When an individual releases the latching mechanisms of such a park brake system the connecting linkages and the park brake actuator move in their disengaging directions until the return bumper contacts the return stop and their motion is stopped. Many constructions of such park brake systems are constructed in such a manner and operated in such a manner that, when the latching mechanisms of the park brake system are released, the connecting linkages and the park brake actuator develop considerable velocity as they travel in their disengaging direction. In such a situation the connecting linkages and the park brake actuator often have considerable velocity when the return bumper contacts the return stop and their velocity is dissipated almost instantaneously at that point. When the connecting linkages and the park brake actuator have such high velocity when the return bumper hits the return stop, large impact forces occur within the connecting linkages and/or the park brake actuator and the return stop. These large impact forces can have adverse effects upon the durability of the park brake system. Undesirably loud noises can also be generated when the return bumper impacts the return stop with such considerable magnitude. Many prior art park brake systems were constructed with means for adjusting the magnitude of the force applied to the connecting linkages by the return spring and users often adjusted the systems so that the forces applied to the connecting linkages by the return spring were very low. As a result, the impact forces in the park brake system when the return bumper contacts the return stop were relatively low for park brake systems adjusted such that the forces applied to the connecting linkages by the return spring were relatively low. Unfortunately, in many instances users adjusted the park brake system such that the return spring applied forces to the connecting linkages of a magnitude insufficient to ensure proper operation of the park brake system. For this reason, recent incarnations of park brake systems have been constructed in such a manner that the return spring applies relatively large forces to the connecting linkages and also in such a manner that the magnitude of the forces applied to the connecting linkages by the return spring are not adjustable by a user.
As a result, an object of the present invention is to provide a vehicle, a park brake system for the vehicle, and connecting linkages and a park brake actuator for the vehicle that are constructed in such a manner that when the latching mechanisms of the park brake system are released, the return bumper contacts the return stop with reduced velocity and force as compared to prior art park brake systems.
The vehicle of the present invention includes a park brake system that has one or more complimentary pairs of a braking component and a braked component. One of the braking component and the braked component of each complimentary pair of a braking component and a braked component is anchored to a superstructure of the vehicle and the other is anchored to a working component of a drivetrain of the vehicle. Friction material is attached to the braking component and/or the braked component of each complimentary pair of a braking component and a braked component. The park brake system is constructed in such a manner, as is well known, that, the braking component may be selectively positioned in either a released position or a set position. When a braking component is positioned in its released position, the braking component is disposed at a distance from its complimentary braked component and the park brake system presents no resistance to movement of the working components of the drivetrain relative to the superstructure of the vehicle. When a braking component is positioned in its set position the friction material attached to the braking component and/or its complimentary braked component is compressed with substantial force between the braking component and its complimentary braked component. Thus, when a braking component is in its set position, relative movement between the braking component and its complimentary braked component is resisted by considerable frictional forces between the braking component and the braked component and, thus, relative movement between the superstructure of the vehicle and the working component of the drivetrain to which the braking component and the braked component are engaged is also resisted. The park brake system thus has two operational statesxe2x80x94set and released. When the braking component of the park brake system is in its set position, the park brake system is in its set operational state and inadvertent movement of the vehicle is prevented. When the braking component of the park brake system is in its released position the park brake system is in its released operational state and, barring other factors which might prevent the vehicle from moving, the vehicle can be driven freely.
The park brake system of the present invention also includes a park brake actuator and connecting linkages that connect the park brake actuator to the braking component of the park brake system. The connecting linkages and the park brake actuator are constructed and engaged to one another and the braking component in such a manner that, when the park brake actuator is moved in an engaging direction the connecting linkages are caused to move in an engaging direction and the connecting linkages, in turn, drive the braking component toward its set position. The connecting linkages and the park brake actuator are further constructed and engaged to one another and the braking component in such a manner that, when the park brake actuator is moved in a disengaging direction, which is opposite its engaging direction, the connecting linkages are caused or allowed to move in their disengaging direction, which is opposite their engaging direction. When the connecting linkages are caused or allowed to move in their disengaging direction, the braking component is caused or allowed to move toward its released position.
The park brake system of the present invention further includes mechanisms to prevent undesirable inadvertent change of the operational state of the park brake system. In order that the park brake system is maintained in its released operational state unless an individual takes action to put the park brake system in its set operational state, the park brake system includes a return spring. The return spring of the park brake system has one end attached directly or indirectly to the superstructure of the vehicle and the other end attached to the connecting linkages of the park brake system in such a manner that the return spring always urges the connecting linkages and, thus, the park brake actuator in their disengaging direction. For purposes of this disclosure, a first component that is engaged, attached, or anchored indirectly to a second component is engaged, attached, or anchored to the second component through intermediate components. The construction of the park brake system with such a return spring ensures that the park brake actuator and the connecting linkages will not inadvertently move in their engaging direction and cause the park brake to assume its set operational state. As a result of this construction it is necessary for an individual manipulating the park brake actuator in its engaging direction to overcome the forces applied to the connecting linkages by the return spring. In order that the park brake system may be maintained in its set operational state without the attention of an individual, the park brake system includes one or more latching mechanisms. The latching mechanisms can be engaged between the superstructure of the vehicle and either the connecting linkages or the park brake actuator to balance the force in the return spring and, thus prevent the return spring from driving the connecting linkages and the park brake actuator in their disengaging direction. The latching mechanisms can also be released when an individual desires to put the park brake system in its released operational state. The park brake system further includes a return stop to limit the travel of the park brake actuator and the connecting linkages in their disengaging direction. The return stop is structure that is anchored directly or indirectly to the superstructure of the vehicle. The return stop is positioned such that at some point in the travel of the park brake actuator and the connecting linkages in their disengaging direction some part of the park brake actuator or the connecting linkages comes into abutment with the return stop and further travel of the connecting linkages and the park brake actuator in their disengaging direction is prevented. The part of the connecting linkages or the park brake actuator of the system that contacts the return stop and, thus, limits the travel of the connecting linkages and the park brake actuator being, as was mentioned above, the return bumper of the park brake system.
The park brake system of the present invention includes an impact reduction energy absorber for reducing the magnitude of the impact in the park brake system when the return bumper contacts the return stop. A first end of the impact reduction energy absorber is attached to either the park brake actuator or a component of the connecting linkages and a second end of the park brake actuator is connected to either the superstructure of the vehicle directly or indirectly or a component of the connecting linkages to which the first end of the impact reduction energy absorber is not attached. The impact reduction energy absorber acts to reduce the impact in the park brake system, when the return bumper contacts the return stop, in one of two ways. An impact reduction energy absorber that is connected between the superstructure of the vehicle and either the connecting linkages or the park brake actuator absorbs some of the energy transferred to the connecting linkages by the return spring while the connecting linkages and the park brake actuator are traveling in their disengaging direction toward the return stop. By absorbing some of the energy transferred to the connecting linkages while they are moving in their disengaging direction, the impact reducing energy absorber causes the connecting linkages and the park brake actuator to have diminished velocity when the return bumper contacts the return stop and, thus, the magnitude of the impact in the park brake system when the return bumper and return stop contact one another is diminished. An impact reduction energy absorber that is connected between components of the connecting linkages absorbs some of the energy transferred to the connecting linkages by the return spring in a short time period starting when the return bumper and the return stop contact one another. By absorbing energy when the return bumper and the return stop contact one another, such an impact reducing energy absorber also diminishes the magnitude of the impact in the park brake system when part of the connecting linkages or the park brake actuator contacts the return stop.